let myString = "Hello";
let myNumber = 10;
let myFloat = 3.14;
let myBoolean = true;
let myNull = null;
let myUndefined; 
let myObject = {name :"alex"};
let myArray = [1,2,3];

console.log(typeof myString);   // 输出: string
console.log(typeof myNumber);   // 输出: number
console.log(typeof myBoolean);  // 输出: boolean
console.log(myNull);            // 输出: null
console.log(myUndefined);       // 输出: undefined
console.log(myObject);          // 输出: { name: 'alex' }
console.log(myArray);           // 输出: [ 1, 2, 3 ]